Cardiac rhythm management devices can include implantable or other ambulatory devices, such as pacemakers, cardioverter-defibrillators, cardiac resynchronization therapy (CRT) devices, or devices that can monitor one or more physiological parameters, or provide one or a combination of pacing, defibrillation, or cardiac resynchronization therapies, or that can both monitor one or more physiological parameters and provide therapy. In an example, such devices can be configured for use with a plurality of implanted or external electrodes, such as to detect or treat cardiac, respiratory, or other conditions. Information obtained, such as using the electrodes, can be used to provide a diagnosis or predict an impending disease state, or to initiate or adjust therapy.
Early detection of physiological conditions that can indicate heart failure (“HF,” sometimes referred to as congestive heart failure, “CHF”), such as before a patient experiences cardiac decompensation associated with such heart failure, can help to indicate treatment that may prevent cardiac decompensation from occurring. Zhao et al., in U.S. Patent Publication No. 2010/0004712, entitled SYSTEMS AND METHODS FOR USE BY AN IMPLANTABLE MEDICAL DEVICE FOR DETECTING HEART FAILURE BASED ON THE INDEPENDENT INFORMATION CONTENT OF IMMITANCE VECTORS, refers to detecting heart failure based on independent informational content of a plurality of immittance vectors, and controlling a function based on the amount of independent informational content. (See Zhao et al. at paragraph [0008].)
Accurate and efficient posture detection can help to provide important information to a clinician or a cardiac rhythm management device, such as to ensure accurate interpretation of one or more physiological parameters, or to determine a therapy. Maile et al., in U.S. Pat. No. 7,559,901, entitled DETERMINING A PATIENT'S POSTURE FROM MECHANICAL VIBRATIONS OF THE HEART, refers to determining a patient's posture by monitoring heart sounds. (See Maile et al. at the Abstract.)